Reaction kinetics investigation of 1-fluoro-2,4-dinitrobenzene with substituted anilines in ethyl acetate-methanol mixtures using linear and nonlinear free energy relationships

Article abstract of DOI:10.1002/poc.1861

Aromatic nucleophilic substitution reaction of 1-fluoro-2,4-dinitrobenzene with para-substituted and meta-substituted anilines was kinetically investigated in the mixtures of ethyl acetate and methanol at room temperature. The correlation of second-order rate coefficients with Hammett's substituent constants yields a fairly linear straight line with negative slope in different mole fractions of ethyl acetate-methanol mixtures. The measured rate coefficients of the reaction demonstrated a dramatic variation in ethyl acetate-methanol mixtures with the increasing mole fraction of ethyl acetate. Linear free energy relationship (LFER) investigations confirm that polarity has a major effect on the reaction rate whereas the hydrogen-bonding ability of the media has a slight effect on it. Nonlinear free energy relationship based on preferential solvation hypothesis showed differences between the microsphere solvation of the solute and the bulk composition of the solvents, and non-ideal behavior is observed in the trend of the rate coefficients, which cover the LFER results. Copyright

Full text of DOI:10.1002/poc.1861

Research Article
Received: 16 November 2010,
Revised: 31 January 2011,
Accepted: 8 March 2011,
Published online in Wiley Online Library: 9 May 2011
(wileyonlinelibrary.com) DOI 10.1002/poc.1861
Reaction kinetics investigation of 1‐fluoro‐2,
4‐dinitrobenzene with substituted anilines in
ethyl acetate–methanol mixtures using linear
and nonlinear free energy relationships
Javad Jamali‐Paghaleha, Ali Reza Harifi‐Moodb
and Mohammad Reza Gholamia*
Aromatic nucleophilic substitution reaction of 1‐fluoro‐2,4‐dinitrobenzene with para‐substituted and meta‐
substituted anilines was kinetically investigated in the mixtures of ethyl acetate and methanol at room temperature.
The correlation of second‐order rate coefficients with Hammett’s substituent constants yields a fairly linear straight
line with negative slope in different mole fractions of ethyl acetate–methanol mixtures. The measured rate coefficients
of the reaction demonstrated a dramatic variation in ethyl acetate–methanol mixtures with the increasing mole
fraction of ethyl acetate. Linear free energy relationship (LFER) investigations confirm that polarity has a major effect
on the reaction rate whereas the hydrogen‐bonding ability of the media has a slight effect on it. Nonlinear free energy
relationship based on preferential solvation hypothesis showed differences between the microsphere solvation of the
solute and the bulk composition of the solvents, and non‐ideal behavior is observed in the trend of the rate
coefficients, which cover the LFER results. Copyright © 2011 John Wiley & Sons, Ltd.
Supporting information may be found in the online version of this paper.
Keywords: aromatic nucleophilic substitution reaction; Hammett equation; preferential solvation; solvent effects; solvent–
solvent interactions
solvent mixtures.[2–8,12–17] Aniline derivatives have been used
recently as nucleophiles in the aromatic nucleophilic substitution
INTRODUCTION
Solvents play a key role in many chemical and physical processes
(reaction rates, selectivity, chemical equilibria, position and intensity
of spectral absorption bands).[1,2] In addition to the solvents, others
such as the effect of the aromatic ring substituents,[3–6] ring size of
the nucleophile,[7] and the electronic nature and position of the
substituents[8] affect the rate of the aromatic nucleophilic substitu-
tion reactions.
reactions.[18,19] We therefore choose the reaction of 1‐fluoro‐2,
4‐dinitrobenzene with meta‐substituted and para‐substituted
anilines in ethyl acetate–methanol mixture to study the solvent
effects and the Hammett parameters on the rate coefficient. In
addition, the rate coefficients data were interpreted according to
solvent effects and preferential solvation as a linear and nonlinear
model, respectively.
Some of the factors that affect the reaction rates are closely related
to the nature and extent of solute–solvent interactions (the solvation
effect) locally developed in the immediate vicinity of the solute,
solvent–solvent interactions (the general medium effect), and
solute–solute interactions (the intersolute effects).[9–13] In mixed
solvents, solute–solvent interactions are much more complex than
solvent–solvent interactions because of the possibility of preferential
solvation by any of the solvent present in the mixture.[9] On the other
hand, solvent–solvent interactions can strongly affect solute–solvent
interactions. The problem is to identify and assess the relative
importance of various factors on the solvent effects for studying on
the reaction rates.[14] The solvent effect on a typical property is
described by a general correlation model, which gives a simulta-
neous separate calculation of the contributions of nonspecific
solute–solvent interactions (such as polarity and polarizability) and
specific solute–solvent interactions (such as electron donor–
acceptor and hydrogen‐bond donor–acceptor abilities).[1,2,11,15]
Numerous studies have been carried out on the reaction of
nitroaryl derivatives with primary and secondary amines in
RESULTS AND DISCUSSION
Reactions of 1‐fluoro‐2,4‐dinitrobenzene with some substituted
anilines (indicated in Table 1) were studied at 25 °C in ethyl acetate
and methanol mixtures. Ethyl acetate was taken as the hydrogen‐
bond acceptor (HBA) and methanol as the hydrogen‐bond donor
(HBD) and an HBA species. In addition to solute–solvent
* Correspondence to: Mohammad Reza Gholami, Department of Chemistry, Sharif
University of Technology, PO Box 11365‐9516, Azadi Ave., Tehran, Iran.
E‐mail: gholami@sharif.edu
a J. Jamali‐Paghaleh, M. R. Gholami
Department of Chemistry, Sharif University of Technology, Azadi Ave.,
Tehran, Iran
b A. R. Harifi‐Mood
Department of Chemistry, Tarbiat Moallem University, Karaj, Iran
J. Phys. Org. Chem. 2011, 24 1095–1100
Copyright © 2011 John Wiley & Sons, Ltd.

J. JAMALI‐PAGHALEH, A. R. HARIFI‐MOOD AND M. R. GHOLAMI
Table 1. Second‐order coefficients (kA, M−1 s−1) for the reaction of anilines with 1‐fluoro‐2,4‐dinitrobenzene in various mole
fraction of ethyl acetate in methanol at 25 °C
Substituents in
aniline
Mole fraction of ethyl acetate
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
None (103 × kA)
p‐Me (103 × kA)
p‐OMe (102 × kA)
p‐OH (102 × kA)
p‐NHCOMe (103 × kA)
p‐NH2 (10 × kA)
p‐COOH (105 × kA)
p‐Cl (104 × kA)
15.8
77.0
15.5
21.2
17.3
13.4
50.5
16.1
15.0
17.3
80.1
78.6
11.8
61.2
11.9
17.3
12.4
10.3
34.0
10.9
8.50
5.92
5.06
22.2
4.56
9.18
5.26
4.81
4.61
19.2
3.95
16.7
3.25
14.5
2.47
11.3
1.44
6.04
1.03
2.16
1.54
1.16
3.05
0.814
0.731
1.61
6.69
6.40
0.203
0.420
0.104
0.217
0.305
0.105
0.403
0.082
0.078
0.326
0.951
0.824
43.6
8.64
13.9
8.77
7.81
28.8
5.93
11.2
6.61
5.81
3.67
7.38
4.52
4.05
9.71
2.81
2.66
4.62
2.92
6.15
3.99
3.41
7.92
2.46
2.23
4.05
2.32
5.18
3.35
2.72
6.79
2.12
1.81
3.38
1.82
3.75
2.73
2.16
5.21
1.72
1.34
2.81
23.4
15.7
12.2
7.02
6.77
9.35
43.5
44.2
4.65
4.42
6.66
32.8
35.0
3.41
3.18
5.35
25.5
27.6
p‐Br (104 × kA)
9.72
m‐Me (103 × kA)
m‐OMe (104 × kA)
m‐OH (104 × kA)
12.7
57.6
58.4
21.1
23.4
17.7
19.1
15.2
10.0
11.9
12.2
NH2
H
F
F
H
NO2
NO2
NO2
H
N
k2
NO2
N
k1
+
_
+
k-1
k3[B]
X
NO2
NO2
X
X
Scheme 1.
interactions, the acidic hydrogen atom of methanol can readily
form a complex with the oxygen atom of ethyl acetate, which in
turn can affect the reaction rate.
The gross mechanism of these reactions in all solvents is given in
Scheme 1.[3–6] The breakdown of the zwitterionic intermediate can
occur spontaneously or by a base‐catalyzed mechanism. The
application of the steady‐state hypothesis to the gross mechanism
shown in Scheme 1 gives Equation (1), where kA is the observed
second‐order rate coefficient and B is aniline as a base catalyst.
compounds.[17,21–24] Both inductive and resonance effects deter-
mine the kind of substituents. The substituents can have either an
electron‐withdrawing or an electron‐donating effect. The former
decreases the electron density of the aromatic ring whereas the
latter has an increase effect. The Hammett constant (σ) reflects the
effects of both inductive and resonance effects on substituents.
Values of σ were taken from Hansch et al.[25] The Hammett
correlations were tested for the reaction between 1‐fluoro‐2,4‐
dinitrobenzene with substituted anilines in the solvent mixture. A
typical plot of Hammett correlations is shown in Figure 1, which
demonstrates a good linear behavior with negative slope, and its
k1ðk2 þ k3½BꢀÞ
kA ¼
(1)
k−1 þ k2 þ k3½Bꢀ
Both the formation of the intermediate and its decomposition
to products can be a rate‐limiting step. If k− 1 < < (k2 + k3[B]), then
kA = k1, thus the reaction is not base catalyzed, and the
formation of the intermediate is the rate‐limiting step;
otherwise, the reactions proceed through the base catalysis.
The second‐order rate coefficients of the reactions under pseudo‐
first‐order conditions with excess of parent aniline were deter-
mined at different mole fractions of ethyl acetate in methanol, and
the results are summarized in Table 1. The selection of mole
fractions was based on the fact that the applied solvatochromic
parameters were available in the literatures.[16] This solvatochromic
parameters represent solute–solvent interactions (so‐called empir-
ical scales), such as normalized polarity (ETN), dipolarity–polarizabil-
ity (π*), and HBD (α) and HBA ability (β).[20] These parameters have
been used to explain variations of the reaction rate by modifying
the reaction media.
Structure–reactivity correlation
The Hammett correlation classically is applied to predict the effects
of substituents on reaction‐rate constants between organic
Figure 1. Typical Hammett plot of logkA versus constant σ for the
reaction in the solvent mixtures (x2 is the mole fraction of ethyl acetate)
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Copyright © 2011 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2011, 24 1095–1100

ETHYL ACETATE–METHANOL MIXTURES
Table 2. Hammett’s parameters for the reaction of 1‐fluoro‐2,4‐dinitrobenzene with substituted anilines in the mixture of ethyl
acetate and methanol at 25 °C
a
x2
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
ρ
−3.451
0.982
−3.537
0.980
−3.591
0.979
−3.635
0.976
−3.673
0.974
−3.678
0.973
−3.677
0.973
−3.690
0.978
−3.655
0.972
−3.664
0.969
−3.498
0.938
R2
ax2 is the mole fraction of ethyl acetate.
Table 3. Statistical (R2, SD), correlation (e, a, and b), and standardized coefficients (SEN , Sα, and Sβ) for correlation of logkA with
T
solvatochromic parameters at 25 °C (11 data were used in these correlations)
N
Substituents in aniline
None
R2
SDa
Const.b
ec
ac
bc
SE
Sα
Sβ
T
0.974
0.998
0.988
0.984
0.994
0.995
0.970
0.995
0.982
0.993
0.998
0.995
0.954
0.997
0.976
0.990
0.998
0.996
0.947
0.996
0.974
0.960
0.994
0.985
0.955
0.996
0.978
0.951
0.996
0.974
0.971
0.997
0.985
0.959
0.984
0.969
0.09
0.03
0.06
0.08
0.06
0.05
0.11
0.05
0.08
0.05
0.03
0.04
0.11
0.03
0.08
0.06
0.03
0.04
0.14
0.04
0.10
0.131
0.05
0.06
0.14
0.05
0.10
0.11
0.03
0.09
0.09
0.03
0.07
0.12
0.08
0.11
−4.55 (0.12)
−5.54 (0.12)
−3.50 (0.37)
−4.36 (0.11)
−5.12 (0.23)
−3.21 (0.29)
−4.00 (0.15)
−5.20 (0.19)
−2.83 (0.52)
−3.56 (0.07)
−4.05 (0.12)
−3.11 (0.25)
−4.35 (0.15)
−5.60 (0.13)
−3.08 (0.48)
−2.91 (0.08)
−3.56 (0.12)
−2.14 (0.25)
−6.38 (0.19)
−7.96 (0.17)
−4.73 (0.60)
−6.13 (0.18)
−7.58 (0.22)
−4.39 (0.50)
−6.18 (0.18)
−7.75 (0.19)
−4.50 (0.59)
−4.31 (0.15)
−5.57 (0.14)
−3.05 (0.50)
−4.92 (0.13)
−5.99 (0.13)
−3.81 (0.42)
−5.02 (0.16)
−6.10 (0.33)
−4.07 (0.63)
3.41 (0.18)
8.07 (0.52)
4.47 (0.39)
4.10 (0.18)
7.71 (1.05)
5.57 (0.30)
3.98 (0.23)
9.63 (0.87)
5.16 (0.55)
3.71 (0.10)
6.00 (0.53)
4.17 (0.26)
3.13 (0.23)
9.03 (0.57)
4.42 (0.51)
3.86 (0.13)
6.93 (0.55)
4.64 (0.26)
3.73 (0.29)
11.18 (0.78)
5.41 (0.63)
4.07 (0.28)
10.89 (0.99)
5.83 (0.52)
4.07 (0.29)
11.49 (0.85)
5.77 (0.62)
3.09 (0.23)
9.04 (0.63)
4.37 (0.52)
3.48 (0.20)
8.54 (0.58)
4.61 (0.44)
3.63 (0.25)
8.76 (1.47)
4.58 (0.67)
—
—
—
—
2.34
1.30
—
1.87
1.27
—
2.39
1.28
—
1.61
1.12
—
2.82
1.38
—
1.79
1.20
—
2.92
1.41
—
2.62
1.40
—
2.76
1.39
—
2.85
1.38
—
2.42
1.30
—
2.37
1.24
—
−1.36
—
—
−0.88
—
—
−1.41
—
—
−0.62
—
—
−1.85
—
—
−0.80
—
—
−1.96
—
—
−1.65
—
—
−1.80
—
—
−1.89
—
—
−1.44
—
—
−1.40
—
—
—
−0.33
—
—
−0.30
—
—
−0.31
—
—
−0.13
—
—
−0.43
—
—
−0.22
—
—
−0.48
—
—
−0.45
—
—
−0.44
—
—
−0.43
—
—
−0.34
—
—
−0.28
−2.43 (0.27)
—
—
−2.86 (0.98)
p‐Me
—
—
−1.88 (0.54)
—
—
−3.13 (0.76)
p‐OMe
—
—
−2.95 (0.45)
—
—
−3.18 (1.38)
p‐OH
—
—
−1.19 (0.28)
—
—
−1.23 (0.66)
p‐NHCOMe
p‐NH2
—
—
−3.08 (0.29)
—
—
−3.45 (1.28)
—
—
−1.60 (0.28)
—
—
−2.11 (0.66)
p‐COOH
p‐Cl
—
—
−3.89 (0.41)
—
—
−4.51 (1.58)
—
—
−3.56 (0.51)
—
—
−4.74 (1.31)
p‐Br
—
—
−3.87 (0.44)
—
—
−4.57 (1.57)
m‐Me
—
—
−3.01 (0.32)
—
—
−3.44 (1.32)
m‐OMe
m‐OH
—
—
−2.64 (0.30)
—
3.02 (1.10)
—
—
−2.68 (0.76)
—
—
−2.56 (1.68)
aStandard deviation.
bIntercept of the single or multiparameter correlation.
ce, a, and b are the coefficients of ETN, α, and β, respectively.
values are summarized in Table 2. The negative sign of the
Hammett slope implies that positive charge develops on the
N‐atom as the transition state is formed. This is expectable in
nucleophilic substitution reactions. The high magnitude of ρ
values suggests preferable influence of nucleophilicity of the
substituted anilines on the reaction rate,[19,26] which confirms
that the formation of the intermediate is the rate‐limiting
step in all solvent compositions.
Solvent–reactivity correlations
In order to determine the incidence of each type of solvent
properties on the kinetics of the reaction, a linear free energy
J. Phys. Org. Chem. 2011, 24 1095–1100
Copyright © 2011 John Wiley & Sons, Ltd.
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J. JAMALI‐PAGHALEH, A. R. HARIFI‐MOOD AND M. R. GHOLAMI
relationship (LFER) correlation based on Kamlet, Abboud and
Taft[27,28] hypothesis was applied. This model is based on the
single or multiparameter correlation between the logk of the
reaction and the solvatochromic parameters of the media.
The data derived from these correlation studies are presented in
Table 3. Multiparameter regression can be usually used, because
combination of some of the solvent properties can affect the
rate coefficient. The second‐order rate coefficients decrease
rapidly with the increasing mole fraction of ethyl acetate
(Table 1). Because changes in solvent polarity and hydrogen‐
bonding interactions are parallel to the variation of the rate
coefficients, each solvent parameter can be effective on the
reaction rate. Single‐parameter correlations of logkA versus ETN in
all composition of the solvents represent a good result, which
indicates that the second‐order rate coefficient of the reactions
increases with the increase of this parameter (Table 3). The
intermediate has a zwitterionic characterization, thus the
reaction rates are accelerated in polar solvents. A dual‐
parameter correlation including HBD and ETN can produce a
better fit compared with the single‐parameter regressions, and
therefore the former is preferred. Figure 2 shows the ability of
the dual‐parameter correlation in the reproduction of the
reaction‐rate coefficients.
Normally, the presence of alkanols decreases the reaction
rate in this type of reaction because of its HBD character;[5,6] in
fact, the low basicity of the aniline derivatives would play a
role in the solvent–nucleophile interactions. Contrary to the
normalized polarity, the HBD ability of solvent reduces the rate
of reaction. Two reasons can be attributed for this reduction.
Firstly, in the presence of aniline or its derivations, methanol is
known to act as an HBD, and there is evidence of strong
hydrogen‐bonding interaction between anilines and methanol.[29]
Therefore, anilines are stabilized via this interaction, and the
reaction rate decreases as the HBD ability of the media
increases. Secondly, ethyl acetate is an HBA molecule, and
methanol is an HBD species in the solvent mixtures. Strong
solvent–solvent interactions in this media can be related to the
hydrogen‐bonding interaction between methanol and ethyl
acetate to give a complex structure that is more or less polar
than the two constituents of mixture.[12,14] This behavior is
attributed to the preferential solvation of solutes by mixed
solvent.[9–14]
Similar correlations were also observed between logkA with
normalized polarity and the HBA ability of the media (Table 3
and Figure 3). The negative effect of the HBA ability of the
solvent on the reaction rate has stark resemblance to that of the
HBD ability.
On the other hand, standardized coefficients of the solvent
properties in all dual‐parameter correlations show that the
nonspecific interactions of the solvent is a preferable and
effective parameter, compared with specific interactions such as
the HBD and HBA abilities of the media.
Preferential solvation model
Interest on preferential solvation as a nonlinear model in mixed
solvents has increased noticeably in recent years.[9–14] The
interpretation of the main features requires simple models that
may describe the behavior of solutes and the structure of binary
solvents. These models may provide valuable solute–solvent and
solvent–solvent structural information. Preferential solvation was
analyzed in this work with the Buhvestov[9,11] models, which are
based on a simple exchange of two solvents according to
Equations (2) and (3)
IðS1Þ2 þ 2S2↔IðS2Þ1 þ 2S1
IðS1Þ2 þ S2↔IðS12Þ2 þ S1
(2)
(3)
where I stands for the solute, S1 and S2 for the pure solvents,
and S12 for the solvent formed by the interaction of solvents 1
and 2. I(S1), I(S2), and I(S12) represent the solute solvated by the
S1, S2, and S12 species. Equation (2) reflects the total exchange
of solvent 1 by solvent 2 in the solvation sphere of the solute,
and Equation 3 corresponds to the exchange by the double‐
structure solvents. The constants of two processes are defined
Figure 2. The plot of calculated logkA versus the experimental values
from dual‐parameter correlation with normalized polarity and hydrogen‐
bond donor ability of the media
Figure 3. The plot of calculated logkA versus the experimental values
from dual‐parameter correlation with normalized polarity and hydrogen‐
bond acceptor ability of the media
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ETHYL ACETATE–METHANOL MIXTURES
Table 4. Parameters from Equation (8) for the mixture of ethyl acetate with methanol for second‐order rate coefficient of the
reaction at 25 °Ca
Substituents in aniline
Y1
Y2
Y12
f2/1
f12/1
SD
R2
None
p‐Me
−1.79
−1.08
−0.791
−0.667
−1.75
0.138
−3.28
−2.77
−2.81
−1.75
−2.09
−2.11
−3.69
−3.38
−2.98
−2.66
−3.52
−1.98
−5.40
−5.09
−5.11
−3.49
−4.02
−4.08
−2.44
−1.87
−1.72
−1.32
−2.44
−0.534
−4.23
−3.68
−3.77
−2.46
−2.82
−3.04
0.178
0.0889
0.0661
0.0745
0.191
0.111
0.103
0.140
0.121
0.159
0.125
0.0375
3.24
2.55
1.82
1.65
3.21
2.39
2.51
3.15
2.66
2.88
2.51
1.32
0.0008
0.0017
0.0005
0.0001
0.0006
0.0003
0.0005
0.0021
0.0008
0.0007
0.0003
0.0044
0.998
0.997
0.999
0.999
0.998
0.999
0.999
0.997
0.999
0.998
0.999
0.991
p‐OMe
p‐OH
p‐NHCOMe
p‐NH2
p‐COOH
p‐Cl
p‐Br
m‐Me
m‐OMe
m‐OH
aY1, Y2, and Y12 are logkA in methanol, ethyl acetate and mixed solvent, respectively.
by the preferential solvation parameters f2/1 and f12/1 according
to Equations (4) and (5)
observed, which have been summarized in Table 4. The ability of
Equation (8) in reproducing the reaction rate coefficients has been
shown in Figure 4. In addition to the good agreement of the data
with preferential solvation model, low f2/1 values show that solutes
are preferentially solvated by methanol. Likewise, the f12/1
parameter reveals that solutes are preferentially solvated by the
mixed solvent in ethyl acetate–methanol mixtures. Preferential
solvation arises whenever the bulk mole fraction solvent compo-
sition differs from the solvation microsphere.[14] Thus, we expect
that free molecules of ethyl acetate are rarely found in the
microsphere solvation of the solutes. The non‐ideal behavior that
was observed for logkA values in these mixtures can be related to
the solvent–solvent interaction. As mentioned before, complex
molecules formed from hydrogen‐bonding interactions between
two solvents, which are preferentially present in the microsphere
solvation of the solutes, solvated strongly the reactants and the
transition state. Therefore, a positive deviation from the ideality is
observed for logkA.
x2s=x1s
ðx20=x10Þ
f2=1
¼
(4)
(5)
2
x1s2=x1s
x20=x10
f12=1
¼
where xis is the mole fraction of the solvent i in the microsphere
solvation of the solute, and xi0 represents the mole fraction of
the solvents in the bulk mixed solvent. The parameters f2/1 and
f12/1 measure the tendency of the solute to be solvated by
solvents S2 and S12 with reference to solvent S1.
Considering that the addition of all different mole fractions
must be equal to unity Equation (6)
x1s þ x2s þ x1s2 ¼ 1
(6)
the mole fractions in the sphere of solvation of solute can be
easily calculated from the preferential solvation parameters and
solvent composition.[30]
The physical property (Y) in the solvent mixtures is calculated
as an average of the properties in pure solvents S1, S2, and S12
(Y1, Y2, and Y12, respectively) according to the mole fractions of
these solvents in the solute’s microsphere of solvation:
Y ¼ x1sY1 þ x2sY2 þ x1s2Y12
(7)
and by substituting x1s, x2s, and x1s2 into Equation (7), the physical
property Y can be evaluated from those of pure solvents, Y1 and
Y2, according to Equation (8).
À
Á
À
Á
À
Á
2
2
Y1 1−x20 þ Y2f2=1 x20 þ Y12f12=1 1−x20 x20
Y ¼
(8)
2
2
ð1−x20Þ þ f2=1ðx20Þ þ f12=1ð1−x20Þx20
The solute–solvent interactions have been widely investi-
gated by using the physical property Y as a solvatochromic
parameter.[9–14,30] In addition, this model can be explained by
applying the free activation energy. Hence, logkA was taken as
Y parameter in Equation (8), and its correlation with solvatochromic
parameters of the solvent was tested. Interesting results were
Figure 4. The typical plot of logkA versus x2. The solid curves have been
calculated from coefficients of Equation (8) given in Table 4, and the
points are experimentally determined
J. Phys. Org. Chem. 2011, 24 1095–1100
Copyright © 2011 John Wiley & Sons, Ltd.
wileyonlinelibrary.com/journal/poc

J. JAMALI‐PAGHALEH, A. R. HARIFI‐MOOD AND M. R. GHOLAMI
EXPERIMENTAL METHODS
Acknowledgement
Materials
The authors thank H. Salari (Sharif University of Technology) for
valuable practical assistance.
Aniline and its derivatives were purchased from Merck (White-
house Station, NJ, USA). The former was purified by vacuum
distillation, and the latter were in analytical grade. Solid
compounds were recrystallized from water/ethanol and water/
acetone. 1‐fluoro‐2,4‐dinitrobenzene (m.p. 26–28 °C) was ob-
tained from Fluka (St. Louis, MO, USA). The solvents methanol
and ethyl acetate were of chromatographic grade and used
without further purification.
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J. Phys. Org. Chem. 2011, 24 1095–1100